1. Field of the Invention
The present invention relates to conveyor systems, and more particularly, to an extensible conveyor for use in association with a continually advancing mine face.
2. Description of the Prior Art
In a typical mining operation such as tunneling, it is well known to use a continuous mining machine, such as a tunnel boring machine, to advance the mine face. The rock material or muck produced by the advancing mining machine can be hauled from the face area by means of conveyor systems which must be extensible to follow the advance of the mining machine. U.S. Pat. No. 4,031,997 to Nelson, issued June 28, 1977, summarizes the various prior art conveyor systems known at that time.
A continuous mining machine would typically have a transfer conveyor belt section for hauling the muck material from adjacent the mining tool to a discharge position a short distance behind the mining machine. An extensible conveyor belt system would typically be arranged to receive the muck as it is being discharged from the transfer conveyor.
Various devices have been suggested for advancing the tail section of the extensible conveyor. Such devices are described in U.S. Pat. Nos. 2,862,604, Craggs et al, issued Dec. 2, 1958; and 3,204,755, Caine, issued Sept. 7, 1965. These systems rely, however, on wire frames which are paid out from a tram or other device and the use of a conveyor belt magazine for tensioning and storing excess lengths of the belt.
Further, it has been found that the discharge of the muck onto the extensible conveyor on the conveying reach of the belt causes stresses by the impact of the falling muck, causing deterioration of the belt.